/*-
 * Copyright 2003-2005 Colin Percival
 * Copyright 2012 Matthew Endsley
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "bsdiff.h"

#include <limits.h>
#include <string.h>

#define MIN(x,y) (((x)<(y)) ? (x) : (y))

static void split(int64_t *I,int64_t *V,int64_t start,int64_t len,int64_t h)
{
  int64_t i,j,k,x,tmp,jj,kk;

  if(len<16) {
    for(k=start;k<start+len;k+=j) {
      j=1;x=V[I[k]+h];
      for(i=1;k+i<start+len;i++) {
        if(V[I[k+i]+h]<x) {
          x=V[I[k+i]+h];
          j=0;
        };
        if(V[I[k+i]+h]==x) {
          tmp=I[k+j];I[k+j]=I[k+i];I[k+i]=tmp;
          j++;
        };
      };
      for(i=0;i<j;i++) V[I[k+i]]=k+j-1;
      if(j==1) I[k]=-1;
    };
    return;
  };

  x=V[I[start+len/2]+h];
  jj=0;kk=0;
  for(i=start;i<start+len;i++) {
    if(V[I[i]+h]<x) jj++;
    if(V[I[i]+h]==x) kk++;
  };
  jj+=start;kk+=jj;

  i=start;j=0;k=0;
  while(i<jj) {
    if(V[I[i]+h]<x) {
      i++;
    } else if(V[I[i]+h]==x) {
      tmp=I[i];I[i]=I[jj+j];I[jj+j]=tmp;
      j++;
    } else {
      tmp=I[i];I[i]=I[kk+k];I[kk+k]=tmp;
      k++;
    };
  };

  while(jj+j<kk) {
    if(V[I[jj+j]+h]==x) {
      j++;
    } else {
      tmp=I[jj+j];I[jj+j]=I[kk+k];I[kk+k]=tmp;
      k++;
    };
  };

  if(jj>start) split(I,V,start,jj-start,h);

  for(i=0;i<kk-jj;i++) V[I[jj+i]]=kk-1;
  if(jj==kk-1) I[jj]=-1;

  if(start+len>kk) split(I,V,kk,start+len-kk,h);
}

static void qsufsort(int64_t *I,int64_t *V,const uint8_t *old,int64_t oldsize)
{
  int64_t buckets[256];
  int64_t i,h,len;

  for(i=0;i<256;i++) buckets[i]=0;
  for(i=0;i<oldsize;i++) buckets[old[i]]++;
  for(i=1;i<256;i++) buckets[i]+=buckets[i-1];
  for(i=255;i>0;i--) buckets[i]=buckets[i-1];
  buckets[0]=0;

  for(i=0;i<oldsize;i++) I[++buckets[old[i]]]=i;
  I[0]=oldsize;
  for(i=0;i<oldsize;i++) V[i]=buckets[old[i]];
  V[oldsize]=0;
  for(i=1;i<256;i++) if(buckets[i]==buckets[i-1]+1) I[buckets[i]]=-1;
  I[0]=-1;

  for(h=1;I[0]!=-(oldsize+1);h+=h) {
    len=0;
    for(i=0;i<oldsize+1;) {
      if(I[i]<0) {
        len-=I[i];
        i-=I[i];
      } else {
        if(len) I[i-len]=-len;
        len=V[I[i]]+1-i;
        split(I,V,i,len,h);
        i+=len;
        len=0;
      };
    };
    if(len) I[i-len]=-len;
  };

  for(i=0;i<oldsize+1;i++) I[V[i]]=i;
}

static int64_t matchlen(const uint8_t *old,int64_t oldsize,const uint8_t *new,int64_t newsize)
{
  int64_t i;

  for(i=0;(i<oldsize)&&(i<newsize);i++)
    if(old[i]!=new[i]) break;

  return i;
}

static int64_t search(const int64_t *I,const uint8_t *old,int64_t oldsize,
const uint8_t *new,int64_t newsize,int64_t st,int64_t en,int64_t *pos)
{
  int64_t x,y;

  if(en-st<2) {
    x=matchlen(old+I[st],oldsize-I[st],new,newsize);
    y=matchlen(old+I[en],oldsize-I[en],new,newsize);

    if(x>y) {
    *pos=I[st];
      return x;
    } else {
    *pos=I[en];
      return y;
    }
  };

  x=st+(en-st)/2;
  if(memcmp(old+I[x],new,MIN(oldsize-I[x],newsize))<0) {
    return search(I,old,oldsize,new,newsize,x,en,pos);
  } else {
    return search(I,old,oldsize,new,newsize,st,x,pos);
  };
}

static void offtout(int64_t x,uint8_t *buf)
{
  int64_t y;

  if(x<0) y=-x; else y=x;

  buf[0]=y%256;y-=buf[0];
  y=y/256;buf[1]=y%256;y-=buf[1];
  y=y/256;buf[2]=y%256;y-=buf[2];
  y=y/256;buf[3]=y%256;y-=buf[3];
  y=y/256;buf[4]=y%256;y-=buf[4];
  y=y/256;buf[5]=y%256;y-=buf[5];
  y=y/256;buf[6]=y%256;y-=buf[6];
  y=y/256;buf[7]=y%256;

  if(x<0) buf[7]|=0x80;
}

static int64_t writedata(struct bsdiff_stream* stream, const void* buffer, int64_t length)
{
  int64_t result = 0;

  while (length > 0)
  {
    const int smallsize = (int)MIN(length, INT_MAX);
    const int writeresult = stream->write(stream, buffer, smallsize);
    if (writeresult == -1)
    {
      return -1;
    }

    result += writeresult;
    length -= smallsize;
    buffer = (uint8_t*)buffer + smallsize;
  }

  return result;
}

struct bsdiff_request
{
  const uint8_t* old;
  int64_t oldsize;
  const uint8_t* new;
  int64_t newsize;
  struct bsdiff_stream* stream;
  int64_t *I;
  uint8_t *buffer;
};

static int bsdiff_internal(const struct bsdiff_request req)
{
  int64_t *I,*V;
  int64_t scan,pos,len;
  int64_t lastscan,lastpos,lastoffset;
  int64_t oldscore,scsc;
  int64_t s,Sf,lenf,Sb,lenb;
  int64_t overlap,Ss,lens;
  int64_t i;
  uint8_t *buffer;
  uint8_t buf[8 * 3];

  if((V=req.stream->malloc((req.oldsize+1)*sizeof(int64_t)))==NULL) return -1;
  I = req.I;

  qsufsort(I,V,req.old,req.oldsize);
  req.stream->free(V);

  buffer = req.buffer;

  /* Compute the differences, writing ctrl as we go */
  scan=0;len=0;pos=0;
  lastscan=0;lastpos=0;lastoffset=0;
  while(scan<req.newsize) {
    oldscore=0;

    for(scsc=scan+=len;scan<req.newsize;scan++) {
      len=search(I,req.old,req.oldsize,req.new+scan,req.newsize-scan,
          0,req.oldsize,&pos);

      for(;scsc<scan+len;scsc++)
        if((scsc+lastoffset<req.oldsize) &&
          (req.old[scsc+lastoffset] == req.new[scsc]))
          oldscore++;

      if(((len==oldscore) && (len!=0)) ||
        (len>oldscore+8)) break;

      if((scan+lastoffset<req.oldsize) &&
        (req.old[scan+lastoffset] == req.new[scan]))
        oldscore--;
    };

    if((len!=oldscore) || (scan==req.newsize)) {
      s=0;Sf=0;lenf=0;
      for(i=0;(lastscan+i<scan)&&(lastpos+i<req.oldsize);) {
        if(req.old[lastpos+i]==req.new[lastscan+i]) s++;
        i++;
        if(s*2-i>Sf*2-lenf) { Sf=s; lenf=i; };
      };

      lenb=0;
      if(scan<req.newsize) {
        s=0;Sb=0;
        for(i=1;(scan>=lastscan+i)&&(pos>=i);i++) {
          if(req.old[pos-i]==req.new[scan-i]) s++;
          if(s*2-i>Sb*2-lenb) { Sb=s; lenb=i; };
        };
      };

      if(lastscan+lenf>scan-lenb) {
        overlap=(lastscan+lenf)-(scan-lenb);
        s=0;Ss=0;lens=0;
        for(i=0;i<overlap;i++) {
          if(req.new[lastscan+lenf-overlap+i]==
            req.old[lastpos+lenf-overlap+i]) s++;
          if(req.new[scan-lenb+i]==
            req.old[pos-lenb+i]) s--;
          if(s>Ss) { Ss=s; lens=i+1; };
        };

        lenf+=lens-overlap;
        lenb-=lens;
      };

      offtout(lenf,buf);
      offtout((scan-lenb)-(lastscan+lenf),buf+8);
      offtout((pos-lenb)-(lastpos+lenf),buf+16);

      /* Write control data */
      if (writedata(req.stream, buf, sizeof(buf)))
        return -1;

      /* Write diff data */
      for(i=0;i<lenf;i++)
        buffer[i]=req.new[lastscan+i]-req.old[lastpos+i];
      if (writedata(req.stream, buffer, lenf))
        return -1;

      /* Write extra data */
      for(i=0;i<(scan-lenb)-(lastscan+lenf);i++)
        buffer[i]=req.new[lastscan+lenf+i];
      if (writedata(req.stream, buffer, (scan-lenb)-(lastscan+lenf)))
        return -1;

      lastscan=scan-lenb;
      lastpos=pos-lenb;
      lastoffset=pos-scan;
    };
  };

  return 0;
}

int bsdiff(const uint8_t* old, int64_t oldsize, const uint8_t* new, int64_t newsize, struct bsdiff_stream* stream)
{
  int result;
  struct bsdiff_request req;

  if((req.I=stream->malloc((oldsize+1)*sizeof(int64_t)))==NULL)
    return -1;

  if((req.buffer=stream->malloc(newsize+1))==NULL)
  {
    stream->free(req.I);
    return -1;
  }

  req.old = old;
  req.oldsize = oldsize;
  req.new = new;
  req.newsize = newsize;
  req.stream = stream;

  result = bsdiff_internal(req);

  stream->free(req.buffer);
  stream->free(req.I);

  return result;
}

#if defined(BSDIFF_EXECUTABLE)

  #include <sys/types.h>

#include <bzlib.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static int bz2_write(struct bsdiff_stream* stream, const void* buffer, int size)
{
  int bz2err;
  BZFILE* bz2;

  bz2 = (BZFILE*)stream->opaque;
  BZ2_bzWrite(&bz2err, bz2, (void*)buffer, size);
  if (bz2err != BZ_STREAM_END && bz2err != BZ_OK)
    return -1;

  return 0;
}

int main(int argc,char *argv[])
{
  int fd;
  int bz2err;
  uint8_t *old,*new;
  off_t oldsize,newsize;
  uint8_t buf[8];
  FILE * pf;
  struct bsdiff_stream stream;
  BZFILE* bz2;

  memset(&bz2, 0, sizeof(bz2));
  stream.malloc = malloc;
  stream.free = free;
  stream.write = bz2_write;

  if(argc!=4) errx(1,"usage: %s oldfile newfile patchfile\n",argv[0]);

  /* Allocate oldsize+1 bytes instead of oldsize bytes to ensure
   that we never try to malloc(0) and get a NULL pointer */
  if(((fd=open(argv[1],O_RDONLY,0))<0) ||
    ((oldsize=lseek(fd,0,SEEK_END))==-1) ||
    ((old=malloc(oldsize+1))==NULL) ||
    (lseek(fd,0,SEEK_SET)!=0) ||
    (read(fd,old,oldsize)!=oldsize) ||
    (close(fd)==-1)) err(1,"%s",argv[1]);


  /* Allocate newsize+1 bytes instead of newsize bytes to ensure
   that we never try to malloc(0) and get a NULL pointer */
  if(((fd=open(argv[2],O_RDONLY,0))<0) ||
    ((newsize=lseek(fd,0,SEEK_END))==-1) ||
    ((new=malloc(newsize+1))==NULL) ||
    (lseek(fd,0,SEEK_SET)!=0) ||
    (read(fd,new,newsize)!=newsize) ||
    (close(fd)==-1)) err(1,"%s",argv[2]);

  /* Create the patch file */
  if ((pf = fopen(argv[3], "w")) == NULL)
    err(1, "%s", argv[3]);

  /* Write header (signature+newsize)*/
  offtout(newsize, buf);
  if (fwrite("ENDSLEY/BSDIFF43", 16, 1, pf) != 1 ||
    fwrite(buf, sizeof(buf), 1, pf) != 1)
    err(1, "Failed to write header");


  if (NULL == (bz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)))
  errx(1, "BZ2_bzWriteOpen, bz2err=%d", bz2err);

  stream.opaque = bz2;
  if (bsdiff(old, oldsize, new, newsize, &stream))
  err(1, "bsdiff");

  BZ2_bzWriteClose(&bz2err, bz2, 0, NULL, NULL);
  if (bz2err != BZ_OK)
    err(1, "BZ2_bzWriteClose, bz2err=%d", bz2err);

  if (fclose(pf))
    err(1, "fclose");

  /* Free the memory we used */
  free(old);
  free(new);

  return 0;
}

#endif
